1. Field of the Invention
The present invention relates to a method for preparing phosphor particles which may be used in a broad range of display applications, such as FED, PDP and CRT screens, and more particularly a method for preparing spherical phosphor particles, in which a precursor solution of phosphors is decomposed to solid particles by aerosol pyrolysis and rapid cooling and subsequently the solid particles are heat-treated at high temperature so that phosphor particles exhibiting improved luminance property can be formed in spherical shape.
2. Description of the Prior Art
The phosphors are conventionally prepared by the combustion method which involves pulverizing process, such as grinding and ball milling. Though the combustion method has the advantage in cost and efficiency in mass production, the phosphors produced thereby contain some raw materials due to the incomplete reaction among different solid materials and further are apt to be contaminated by impurities mixed during the pulverizing process. In addition, the phosphor surface is damaged during the grinding and milling process, resulting in the loss of the emission intensity. Since the properties such as high purity and high luminescent efficiency are required for the phosphors used in HDTV display applications, several alternative synthetic methods, such as sol-gel method or hydrothermal method, have been experimentally tried for achieving the above properties, but those methods have the disadvantage in cost and efficiency in mass production. Recently, pearl-like spherical phosphor particles were prepared by the induction thermal plasma method (Asia Display '95, p 643.about.646), in which raw phosphor particles produced by the combustion method were introduced into the plasma flame at the temperature of several thousand degrees, where the particles are melt, partly evaporated, and then resolidified on subsequent cooling. However, the plasma method may lead to not only change of phosphor composition, but also uneven distribution of luminescent centers in host lattices, resulting in decrease of luminescent efficiency. Furthermore, additional equipments are needed to adopt the plasma method for mass production of the pearl-like spherical phosphor particles.